1. Field of the Invention
The present invention relates, in general, to the field of surveying instruments. More particularly, the present invention relates to an apparatus and method for compensating a laser based surveying instrument for nonvertical mounting structure alignment.
2. Description of the Related Art
Conventional surveying instruments such as Laser Technology, Incorporated's laser based Criterion series surveying instruments are designed for mounting on a stable tripod which is leveled and held stationary directly over the location from which measurements are to be based. Setting up a surveying instrument in this manner, precisely leveled, especially in rugged terrain is a very time consuming process.
First, a suitable site must be found upon which a tripod can be leveled over the precise point on the ground from which measurements are to be taken. Second, the tripod must be set up with the instrument mounting plate at the apex of the tripod level. Third, the level tripod must be oriented with the aid of a plumb bob such that the center of the mounting plate is exactly over the ground point being measured from. Fourth, the instrument mounted on the mounting plate is then aimed at the target. Next, the level and plumb of the instrument base is again checked. Finally, the measurement is taken and the level and plumb of the instrument base is rechecked again. After each rotational or inclinational movement of the instrument the level and plumb of the instrument is also rechecked to ensure that the support structure has not changed. If it has, the instrument base must be re-leveled and re-plumbed.
All of these manipulations require substantial time to perform. What is needed, then, is a mechanism which enables simply setting up the measuring instrument so as to eliminate some or all of the time consuming setup steps just described without sacrificing accuracy of the resulting measurements. Further, an automatic compensation circuit to compensate the measurement automatically for inaccuracies in physical instrument mounting configurations would be highly desirable.